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MFJ-1278B MULTI-MODE APPENDIX B MODEM CALIBRATION
NOTE: If recalibrating the VB modem for Low Tone RTTY, then remove the jumpers from
JMP E, F, G, and H and tune R114 until the 10th LED from the left is lit.
26. Press the SPACE BAR. The MFJ-1278B will display the CMD: prompt. This
indicates the completion of the MFJ-1278B MODULATOR and DEMODULATOR
CALIBRATION.
If there any problems or difficulties with this procedure, feel free to contact our Technical
Staff at 1-800-647-8324, and they will be more than happy to help you.
Calibration Method II
The MFJ-1278B Modulator and Demodulator Calibration with CALSET. The below
procedure needs no test equipment, and is accurate if done properly. This procedure relies on
the internal calibration routine, that uses the STA and CON leds as calibration indicators. Be
sure to follow each step carefully. If any problems arise, please go back and check the
preceeding step, to make sure it works as specified.
Calibration Procedure:
Calibration Method II is a three (3) step process. The three steps areas follows:
1. Center the modulator tones over the required modem center frequency (Fc).
2. Align the demodulator center frequency.
3. Align the tuning indicator.
NOTE:ALL THREE STEPS SHOULD BE PERFORMED IN THE ABOVE ORDER!
If they are not all done at the same time, or in the correct order, the modem may not be
receiving and transmitting on the same frequency, and the tuning indicator may give false
indications.
The third step, alignment of the tuning indicator, should only be used in conjunction with
alignment of the 300 baud 200 Hz shift demodulator.
The other AFSK modems available in the MFJ-1278B can be aligned using exactly the same
steps presented here but substituting the appropriate part numbers for the adjustments.
However, do NOT align the tuning indicator to anything but the 300 baud 200 Hz shift HF
packet modem.